[PATCH] drm/amd/display: avoid null pointer dereference in dm_set_vblank

[Defang Bo]

[Why]
Similar to commit<dddc0557e3a0>("drm/amd/display: Guard against null crtc in CRC IRQ"), a null pointer deference can occur if crtc is null in
dm_set_vblank.

[How]
Check that CRTC is non-null before accessing its fields.

Signed-off-by: Defang Bo <bodefang@xxxxxxx>
---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index e2b23486..f820962 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -4875,11 +4875,19 @@ static inline int dm_set_vupdate_irq(struct drm_crtc *crtc, bool enable)
 static inline int dm_set_vblank(struct drm_crtc *crtc, bool enable)
 {
 	enum dc_irq_source irq_source;
-	struct amdgpu_crtc *acrtc = to_amdgpu_crtc(crtc);
-	struct amdgpu_device *adev = drm_to_adev(crtc->dev);
-	struct dm_crtc_state *acrtc_state = to_dm_crtc_state(crtc->state);
+	struct amdgpu_crtc *acrtc;
+	struct amdgpu_device *adev;
+	struct dm_crtc_state *acrtc_state;
 	int rc = 0;
 
+	if (crtc == NULL)
+		return -EINVAL;
+
+	acrtc = to_amdgpu_crtc(crtc);
+	adev = drm_to_adev(crtc->dev);
+	acrtc_state = to_dm_crtc_state(crtc->state);
+
+
 	if (enable) {
 		/* vblank irq on -> Only need vupdate irq in vrr mode */
 		if (amdgpu_dm_vrr_active(acrtc_state))
-- 
2.7.4